phpjs/experimental/math/srand.js

php.js offers community built php functions in javascript

function srand(seed) {
  // http://kevin.vanzonneveld.net
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // -    depends on: gettimeofday
  // -    depends on: time
  // %          note 1: This is a very possibly imperfect adaptation from the PHP source code
  // %          note 2: In order for this to work, the commented out portion in rand() must be used instead of the default JS-based implementation
  // *     example 1: srand(13450);
  // *     returns 1: undefined
  // *     example 2: srand();
  // *     returns 2: undefined

  var s1, s2, that = this;

  // BEGIN REDUNDANT
  this.php_js = this.php_js || {};
  // END REDUNDANT
  // php_srand
  var lcg_seed = function() {
    try {
      var tv = that.gettimeofday();
      s1 = tv.sec ^ (~tv.usec);
    }
    catch (e) {
      s1 = 1;
    }
    s2 = Math.random(); // instead of tsrm_thread_id() or getpid()
    this.php_js.seeded = 1;
  };

  var MODMULT = function(a, b, c, m, s) {
    var q = s / a;
    s = b * (s - a * q) - c * q;
    if (s < 0) {
      s += m;
    }
    return s;
  };
  var php_combined_lcg = function() {
    if (!this.php_js.seeded) {
      lcg_seed(); // should only be run once
    }
    s1 = MODMULT(53668, 40014, 12211, 2147483563, s1);
    s2 = MODMULT(52774, 40692, 3791, 2147483399, s2);

    var z = s1 - s2;
    if (z < 1) {
      z += 2147483562;
    }
    return z * 4.656613e-10;
  };
  this.php_js.rand_seed = seed ||
      (parseInt(this.time() * Math.random(), 10) ^ parseInt(1000000.0 * php_combined_lcg(), 10)); // php_rand.h: GENERATE_SEED(); using Math.random() instead of getpid
}